The ancient horseshoe crab has bright blue blood. It uses copper-based haemocyanin instead of iron, allowing it to carry oxygen efficiently in cold ocean waters. Octopuses also have blue blood. Living ...

Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world. Most people picture blood as red: bright and oxygen-rich ...

Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world. Blue blood may look alien, but it’s one of evolution’s most ...